Use arc4random on BSD systems to avoid complaints from the compiler

fiche.c

@@ -24,6 +24,7 @@ $ cat fiche.c | nc localhost 9999
 -------------------------------------------------------------------------------
 */
 
+#include <sys/param.h>
 #include "fiche.h"
 
 int main(int argc, char **argv)
@@ -271,13 +272,21 @@ void generate_url(char *buffer, char *slug, size_t slug_length, struct client_da
 
     for (i = 0; i <= SLUG_SIZE - 1; i++)
     {
+#if defined(BSD)
+	int symbol_id = arc4random() % strlen(symbols);
+#else
         int symbol_id = rand_r(&time_seed) % strlen(symbols);
+#endif
         slug[i] = symbols[symbol_id];
     }
 
     while (create_directory(slug) == -1)
     {
+#if defined(BSD)
+	int symbol_id = arc4random() % strlen(symbols);
+#else
         int symbol_id = rand_r(&time_seed) % strlen(symbols);
+#endif
         slug[strlen(slug)] = symbols[symbol_id];
     }